Even the first time I played ME2, I realized that it had a lot to say about how to make supporting characters fully-realized, three-dimensional beings. But this time, re-experiencing Mordin Solus’s loyalty mission, I finally really, thoroughly, utterly understood two things.

Fuck anybody who says that video games aren’t art.

Every character is the hero of their own story.

We hear #2 all the time. On the scale of repeated-unto-banality writing advice, it probably ranks just under “Write what you know!” I know that I’ve heard it many, many times, but I don’t think it ever fully clicked until Mordin was standing over the corpse of a female krogan, raw with fury at her meaningless death.

For reference, Dr. Mordin Solus would basically be Space Mengele to the krogans, if everything he did hadn’t been kept top secret. He led a team of scientists that adapted a bioengineered plague to ensure the continued sterility of most of the krogan population. He did this to make sure that the krogan, who are hulking dinosaur aliens with two auxiliary organ systems and massive regenerative abilities, wouldn’t breed so fast that they overwhelm the galaxy. And that’s what most of the other characters in the game world focus on—the plague, called the genophage, is monstrous. And rightly so, because it strips the vast majority of krogans of the ability to reproduce.

Then you go on Mordin’s loyalty mission, and you discover the other side of the coin. That when he led the team to design the plague, he didn’t just have krogan sterility as a goal.

He wanted to preserve the krogan people.

What he did—the impossible decision he had to make, that still leaves him unable to sleep some nights—was to ensure the genophage stabilized the krogan population. It was a horrible thing, but Mordin took that guilt upon himself because it was the only way he could see that the krogan and the rest of the galaxy could coexist. The alternatives were to completely sterilize the krogans, thereby committing genocide, or to allow the krogans to breed out of control and run roughshod across the galaxy, leading to massive war from one end of the Milky Way to the other.

Mordin Solus took the third option, and he struggles with that choice throughout the entire mission. And he is disgusted that someone experimented on a live krogan in an attempt to cure the genophage. Mordin did his work in simulations, performed high-level tests on animals genetically similar to krogan, but never experimented on a sapient being.

All of this, that I just made you read, this was what made Dr. Mordin Solus more than The Scientist in ME2. He could’ve just stayed a cardboard cutout. “Ah! I see. A fast-talking, blunt genius with a smarter-than-thou attitude. Yes. Never saw one of those before.”

But during that loyalty mission, you see that Mordin feels uncertainty and regret, that he struggles with intractable problems, that he has a deep love of all sapient life. And that he is, for all intents and purposes, an old man looking for some way to soothe a conscience still scarred by the things he had to do in the name of galactic peace.

Now, I’m not saying that you need to burn entire chapters or subplots on each and every supporting character. Video games are a special medium, and role-playing games even more so—they can get away with setting aside an hour for a single character.

But I think that knowing where a character came from and what they’ve done, and letting that influence their actions and decisions… I think that’s the ticket, right there. I think that’ll make sure your supporting characters breathe.